The present invention relates to a stacker for grouping and stacking substantially flat articles, particularly goods or packages of goods in the form of blister packs, into stacks of goods, comprising a goods feeder, a primary packing unit and a unit for supplying or passing on the stacks of articles piled up in multiple layers by the primary packing unit for subsequent secondary packaging or processing, wherein the goods feeder can separate the articles supplied to it and feed them to the primary packing unit in generally controlled manner, one after another and the packing unit has a goods magazine with a goods support, on which the articles, which are inserted in the magazine from above by the feeder, may be superimposed in multiple layers to form stacks of goods, and wherein the completed stacks may be removed from the magazine by means of an ejection unit and fed to the supply unit.
Stackers of this type are known in a general way from packaging technology. In these stackers flat articles--e.g. where medicaments have to be packed, the so-called blister packs, in which individual tablets are welded in between a plastic film and an aluminium sheet--are supplied to a goods magazine by a goods feeder. Packaging lines of this type are usually arranged directly after the production line and immediately apply the primary and secondary packing to the goods just produced. In these lines the individual goods are first aligned one behind the other by suitable separating means, then grouped ready for packing before being passed on to the actual packaging machine.
In the case of flat articles being packed one above the other in cartons or similar packs, the goods arc either grouped directly or first put together in a pre-pack, such as the card-like blister packs for tablets, then finally packed in a re-packing device in the form in which they will be put on the market. For this purpose the stack of goods formed by the stacker is held by a cassette, then the carton of the re-packing device is folded around the stack. The individual articles are supplied to the goods feeder, for example via a hopper or a moving belt of the production line. The parts are then first separated and aligned one behind the other by wipers, reverse motion belts or similar means.
The goods feeder is generally provided with identification means allowing the exact quantities of goods brought into the magazine to be counted or weighed. The desired number of parts to be stacked up is in turn superimposed and aligned in the magazine. When such a stack has been formed for packing or further processing, it is passed to the supply unit by the ejection unit. The ejection unit may for example be in the form of a pressure member by which the completed stack may be slid laterally out of the magazine.
Known stackers however have the disadvantage that the flow of goods camuot be continuous. While the ejection unit is in action the stacking process in the magazine has to stop in order not to interrupt the hand-over of the finished stack. There are thus idle times both at the feeder and in part of the magazine during ejection. This lengthens the processing time and thereby increases operating costs and the capital costs of the stacker.
Another disadvantage is that production lines usually operate continuously, so the material flow to the feed of the stacker is also continuous. Discontinuous operation of the stacker thus requires a material buffer in the region of the feeder, which again necessitates extra expenditure and may be a further source of interference with the flow of material in the packaging line. This drawback has been eliminated in a known further development of the stacker, by the provision of a second primary packing unit, with the two units being charged alternately.
Although continuous operation is possible with this construction, as the stacking process can take place in one packing unit while the ejection unit in the other is passing on the finished stack to the supply unit, it is at the cost of considerable capital expenditure on the extended logistics of the material flow. Thus suitable diversion and re-combining points must be provided, first to divide the stream of goods between the two packing units then to bring them together again after the stacking process. There is thus an increase in expenditure both on the stacker and on the necessary space requirement.
An object of the invention is to provide a stacker where the processing speed is increased at the lowest possible additional cost.